Question

The experiment shown in the figure has been carried out by Morgan to show the phenomenon of linkage and recombination. If in Cross I, genes are tightly linked and in Cross D, genes are loosely linked then what will be the percentage of recombinants produced in Cross I and Cross II respectively?

A) 98.7% and 62.8%
B) 1.3% and 37.2%
C) 37.2% and 1.3%
D) 62.8% and 98.7%

Answer 1

Hint: Cross I and Cross II both produced recombinants, although at different rates (1.3% and 37.2%, respectively).

Complete Step by Step Answer:
The linking phenomenon is this. To create the F1 offspring, Thomas Morgan combined females with yellow bodies and white eyes with men with brown bodies and red eyes. The F1 generation was then crossed with the F2 generation. Cross I was this. He bred wild-type males with white-bodied females that had little wings. Cross II was this. The gene did not follow Mendel's law of independent assortment, he observed.
In cross I
Due to their close genetic relationships, the yellow and white genes revealed a 1.3% recombination rate.
In cross II
Due to their loose connections, the white and tiny genes displayed a recombination rate of 37.2%. Morgan found that the interconnection of genes was to blame. Due to this, linked genes—genes that inherit jointly in the progeny—are the consequence.
Hence, option B is the correct answer.



Note: Gene inheritance is characterised by events such as linkage and recombination. When two or more connected genes are invariably inherited in the same combination for more than two generations, this is referred to be a linkage. The test cross progeny never had recombination frequencies higher than 50%.